Dmitry Gudkov's blog about Business Intelligence and Data Visualization

September 4, 2016

How to use the memstat metrics in QViewer

Starting from version 3.1 QViewer shows two memstat metrics in Table Metadata window:

Size, bytes -- total size of the column in bytes

Avg.bytes per symbol -- average size of column values in byte

click to zoom

These metrics are calculated similarly to memstat data available in QlikView (not available in Qlik Sense so far). Since the structure of QVD files is very close to the internal in-memory data format in Qlik these metrics can be used to optimize (reduce) memory footprint of resident tables which can be desirable for particularly large applications. The most convenient way to inspect resident tables in QViewer is setup a simple generic subroutine as described here. Alternatively, you can insert temporary STORE statements to save resident tables into QVDs and then open them in QViewer manually.

When looking at the memstat metrics in QViewer you would typically want to identify columns that take most of space (hint: click column headers in Table Metadata to sort the grid). A few things that you can do reduce table size:

Remove unnecessary columns that take a lot of space

Force Qlik to convert duals to numbers by multiplying them by 1

Trim text values to remove trailing and leading spaces

Use integers instead of floats where possible

Round up floats to fewer decimal digits to have fewer distinct values in the column

About Dmitry Gudkov

I used to be a BI consultant for 12+ years. In 2013 I switched to developing BI/ETL software and created EasyMorph — a data transformation tool optimized for business users. I'm also the author of QViewer — a popular standalone QVD file viewer.